Responses to operant conditioning in the corn snake, Pantherophis guttatus, using olfactory and visual stimuli

Abstract Operant conditioning experiments have shown that a broad variety of animal species reliably form associations between a reinforced cue and the consequences of choosing it. Once established, these associations can serve as a basis for assessing behavioral flexibility, the ability to alter behavior in response to a change in the environment, by switching which stimulus is reinforced. Snakes are historically underrepresented in such studies. We used reinforcement with food rewards to train two cohorts of corn snakes ( Pantherophis guttatus , 15 snakes in total), to discriminate between two olfactory and two visual cues. We applied a criterion for acquisition of at least 7 correct decisions in any consecutive trials, and for the first cohort tested for reversal learning of olfactory and then visual cues once the criterion was met. Error rates and latencies to correct choices declined significantly in cohort 1. The response of a second cohort of seven snakes was more subtle: all but one reached criterion, but with little overall decline in error rates. When subjected to repeated reversals, cohort 1 responded increasingly quickly to each successive reversal with fewer trials to criterion, demonstrating the cognitive abilities to inhibit learned responses and to switch their attention to the previously irrelevant cue. When their long-term memory of the reinforced visual cues was tested, cohort 1 made correct choices in 95% of trials up to six months after the experiment ended, while cohort 2’s choices were random after three months. Given the limited success of cohort 2 with visual cues alone, cohort 1 may have been primed by its initial exposure to olfactory cues, which are believed to be more ecologically salient for snakes. The response by cohort 1 to initial and serial reversal training is comparable to that seen in other vertebrate species.